1. Field of the Invention
The invention relates generally to the field of determining the level of a fluid in a storage tank. More specifically, the invention relates to an apparatus for measuring the time of receipt for a reflected acoustic wave.
2. Description of the Related Art
The level of a fluid in a storage tank can be measured using various techniques. In one technique, a transducer is connected to the bottom surface of the storage tank. The transducer is excited by a pulse from a function generator. The vibration from the transducer excites a pulsed wave in the fluid within the storage tank, which propagates upward toward the fluid-gas interface, i.e., the interface between the top of the fluid and the gas above the fluid. At the fluid-gas interface, a portion of the wave is reflected back toward the transducer where it is received. Based on the reflected wave, the transducer generates an electrical signal, which is provided to a processing system. The processing system calculates the distance from the transducer to the top of the fluid, and thus, the depth of the fluid in the storage tank, based on the known value of the speed of sound through the fluid and the time measured for the wave to propagate from the transducer to the fluid/air interface and back to the transducer.
Accordingly, an accurate calculation of the depth of the fluid in the storage tank is dependent upon an accurate determination of the time at which the reflected wave is received at the transducer. It should, therefore, be appreciated that there is a need for an ultrasonic measurement system and method that accurately calculates the depth of a fluid in a storage tank by accurately determining the time of receipt of the reflected wave. The present invention satisfies this need.